Surveyor&#39;s rod



Dec. 2, 1930. R. E. KAPPs sURvEYoR's ROD Filed June l, 1929 5 5 w 2 A. t .MO 2... 2/ l? r.. 5

Patented Dec. 2, 1930 UNITED? STATES PATENT OFFICE ROBERT E. KAPIESL OE TROY, NEW YORK, ASSAIGNOR 'IO W. & L. E. GURLEY, OF TROY,`

NEW'r YORK, A CORPORATION, OF NEW YORK sUnvnYoRs 'non f Application lcd June 1, 1929. ISerial No. 387,719. i

This invention relates to surveyors rods of the extensible type, and the purpose of the invention is to produce a precise direct read# ing rod.

The conventional extensible rod consists of two telescoping wooden sections upon which the graduations .aredirectly placed.V Vlien fully extended the rod is direct reading throughout its entire length, but is characterized `by certainserious disadvantages for precise work. In the first place, the wood contracts and expands longitudinally with changes in atmospheric conditions, and this introduces errors which are more orless indeterminate. Attempts to position the parts relatively to each other in their extended relation by means of stops, have proved unsuccessful, and the best practice heretofore has been to use a Vernier, by means of which the adjustment of theV two parts of the rod in extended position isaccurately determined. This method, however, is not free of objection, one source of trouble beingthatjafter the two sections are clamped 'together they slip, and unless the fact is immediatelyudetected, errors are introduced. Unless such a rod is fully extended the upper portion is not direct reading. l

The present invention produces a rod in which the extensible frame is of wood but in which the graduations are not placed upon the wood, but, on the contrary, are placed upon a fiexible tape, preferably a metal tape formed of ainaterial havingapproximately" a Zero coeiiicient of thermal expansion. As an example of suchV aV material, may be mentioned an alloy of nickel and steel containing 361% nickel.' The/use of ametal tape of known coefficient of expansion will however permit accurate correction for thermal` expansion. The tape is fastened to therod only section is a second pulley, and the tape passes- 1800 around this pulley and extends thence upward in an `interval between the two sections of the'rodtoa pointat orneai'fthc upper end of the front section,to the rear face of which itis attached.

In order to keep the tape under a substan-v tially uniform tension so that no error will be introduced by variations in tension, one

of the two pulleys, preferably the second one'` above mentioned, is yieldingly mounted in guides, 'a take-up spring being provided to afford the desired tension,V It is desirable to provide means for adjusting the tension, and

this isconvenieiitly provided by making the upper pulley positively adjustable by means ofa screw or equivalent device. i

There is a substantial advantage in applying the positive adjustment to the first pulley, that is, the one at the top of theA rear section, because the position of this pulley determines the position of the active run of the tape. However, this upper pulleymight be madefixed, if desired, and other means might Vbe provided for adjusting the tension on the tape, as obviously the tension is affected bythe stress` on the take-up spring which is susceptible of adjustment in various ways.

The rod constructed as .above outlined, is direct reading throughout its length, whether fully orpartially extended. This feature is of particular importance in work manently connected to the face of the rodat all times, that it is subject to substantially uniform tension at all times, and that it is free to expand and contract independently of the rod just as the rod is free to expand and contract independently of the tape.

rlhe mechanical structure adopted to accomplish these results is subject to variation, as will be obvious to skilled mechanics.

lhat is claimed is,-

l. A surveyors rod of the extensible type, comprising in combination, an extensible frame structure including two members, one longitudinally slidableV on the other; a pair of guide pulleys mounted on one of said members adjacent the ends thereof; a tape connected at its ends with the other member and free of connection with said frame structure intermediate said points of connection, said tape extending from one point'of connection over the entire length of the front face of said frame structure, thence around onel pulley, thence along the back of the frame structure to and around the other pulley to the other point of connection; and means for placing said tape under substantially,constant tensile stress.

2. A surveyors rod of the extensible type, comprising in combination, an extensible frame structure including two members, one' longitudinally slidable on the other; a pair of guide pulleys mounted on one of said members adjacent the endsv thereof; a tape connected at its ends with the other member and free of connection with said frame structure intermediate said points of connection, said tape extending from one point of connection over the entire length of the front face of said frame structure, thence around one pulley, thence along the back of the frame structure to and around the other pulley to the other point of connection; and a resilient mounting for one of said pulleys. y

3. A surveyors rod of the extensible type, comprising in combination, an extensible frame structure including two members, one longitudinally slidable on the other; a pair of guide pulleys mounted onV one of said' members adjacent the ends thereof; a tape connected at its ends with the other member and free of connection with said frame structure intermediate said points of connection, said tape extending from one point of connection over the entire length of the front face of said frame structure, thence around one pulley, thence along the back of the frame structure to and around the other pulley to the other point of connection; a resilient mounting for one of said pulleys; and a positively adjustable take-up mounting for the other pulley.

4. A surveyors rod of the extensible type, comprising in combination, an extensible frame structure including two members, one longitudinally slidable on the other; a pair of guide pulleys Y mounted on one of said members adjacent the ends thereof; a tape connected at its ends with the other member and free lof connection with said frame structure intermediate said points of connection, said tape extending from one point of connection over the entire length of the front face of said frame structure, thence around one pulley, thence along the back of the frame structure to and around the other pulley to the other point of connection; spring actuated means for placing said tape under tensile stress; and means for adjusting thestress exerted'by the last named means.

5. A surveyors rod of the extensible type, comprising in combination, an extensible frame structure including a lower section provided at its lower end with means for positioning the rod, and an upper section longitudinally slidable on the lower section; a pair of guide pulleys mounted on the upper section adjacent the extremities thereof; a tape connected to the front face of the lower section adjacent the lower end thereof and extending thence free of said frame structure upward over the entire length of the front faces of both sections, thence to the rear over one of said pulleys, down the rear face of the upper section to the second pulley, around the .second pulley and thence to a point adjacent the upper end of the lower section to which it is connected; and means for placing said tape under substantially constant tensile stress. Y

6. A rod of the type defined in claim 1, in which said tape is of metal characterized by a substantially zero coeificient of thermal expansion.

7. A rod of the type defined in claim 5, in which the tape is of a metal having a substantially Zero coefficient of thermal expansion.

8. A Vsurveyors rod of the extensible type, comprising in combination, an extensible frame structure including two members, one longitudinally slidable on the other; a pair of guide pulleys mounted on one of said members adjacent the ends thereof; a tape connected at its ends with the other member and free of connection with said frame structure intermediate said points of connection, said tape extending from one point of connection on the front face of the frame structure, around one pulley, thence along the back of the frame structure to and around the other pulley to the other point of connection; and 'i means Yfor placing said tape 'under substantially constant tensile stress.

9. A surveyors rod of the extensible type, comprising in combination, an extensible frame structure including a lower section provided at its lower end with means for positioning the rod, and an upper section longitudinally slidable on the lower section; a pair of guide pulleys mounted on the upper section adjacent the extremities thereof; a tape ofniaterinl having a substantially Zero Coelieient of thermal expansion connected to the front fece of the lower section in fixed d- Inensionnl relation to said positioning means, and extending thence upward e nd then to the ieai over one of said pulleys, clown the real' face of the upper Section to the second pulley, around the second pulley and thence to a point adjacent the upper end of the lowfi I section to which it is connected; and means for placing Suid tape under substantially constant tensile Stress.

ln testimony whereof I have signed iny nznne to this speeiiieation.

ROBERT E. KAPPS. 

